1. Field of the Invention
The present invention relates to a computer system capable of interruption using a special protection code for the write interruption region of a memory device. The system according to the present invention is applicable to, for example, a central processor unit (CPU) for a microcomputer or minicomputer having a stack function.
2. Description of the Related Art
In general, a subsidiary memory device is used as an address translation buffer memory for a CPU and a main memory in a microcomputer or minicomputer having a stack function. The address translation buffer memory receives a logical address from the CPU and delivers a translated real address and a protection code. The translated real address is supplied to the main memory.
An error detection circuit receives the protection code from the address translation buffer memory and an access instruction code from the CPU to carry out error detection. When an error is detected by the error detection circuit, the information of the error is transmitted to the CPU and the devices to be accessed to prevent the access in question from being executed.
The stack function of the system is related to the stack region in the main memory and the stack pointer controlled by the instruction of the CPU. The scope of the stack region is essentially limited. If the address indicated by the stack pointer proceeds through the entire stack region and further proceeds excessively to the region for the usual program and usual data, that is, if an overflow of the stack operation occurs, there is a problem that the stack data may be written into the region for the usual program and usual data and thus destroy the stored program and data.
Due to this, in the prior art, the system is constructed to prohibit writing operations to the region beyond the stack region.
Accordingly, there has been the disadvantage of suspension of the operation of the CPU, preventing the desired continuation of the system operation, when the stack pointer invades the region beyond the stack region.